Communication systems are known to comprise a plurality of communication units, base stations, and managing terminals, i.e., system controllers. Typically, the base stations and communication units, i.e., communication devices, contain all the software necessary to perform several functions or features of the communication system such as trunking, secure operations, etc. Enabling the necessary software is done by a system controller which may be coupled to the communication device via a modem.
In prior art communication devices, embedded software programs functioned only when the proper hardware was present in the communication device or communication system. As technology advances, communication devices are becoming "plug in boxes" comprising all the hardware and embedded software programs necessary to perform all the required functions and features of the communication system.
Having to build only one type of communication device (for example, base stations or communication units) aids in the manufacturing process, in that opportunities for errors are reduced over building many types of communication devices with different features. With one base station able to perform all functions, a base station becomes an "off the shelf product." To remain affordable and flexible, it is desirable to devise a way to "program" the "off the shelf" communication device to operate with specific functions or features as purchased by a customer. In this manner, customers pay only for the functions or features required for the functionality of their communication system.
To provide customers with only the software functions and features purchased, a method of enabling purchased functions and features while disabling functions and features not purchased is required. In prior art communication systems, this is typically accomplished by using a password to enable premium features within the communication device. This provides some level of protection, however, the same password is used for each communication device which is not difficult to obtain using today's technology. For example, the password may be determined by reading a memory location within the communication device or merely tapping into a communication link. In this manner, a communication device could be upgraded to perform unauthorized premium features with the illicitly obtained password. This easy access to the password results in lost revenue for the manufacturer.
For greater protection, the password may be encrypted and loaded into the communication device where the password is decrypted to determine which features are enabled. In this method, the encryption/decryption schemes used to encrypt/decrypt the password are usually inverse functions of each other. Since the decryption device resides inside the communication device, which is easily accessible, the communication device could be examined, and the encryption/decryption scheme could be discovered. Once the encryption/decryption scheme is discovered, a password could easily be generated, encrypted, and uploaded to a communication device to enable unauthorized premium features. Again resulting in lost revenues for the manufacturer.
Therefore, a need exists for a method utilizing a password that is not easily obtainable, to enable only those software functions and features that a particular customer has purchased and is authorized to use for the functionality of their specific communication system.